Artificial leather and process of manufacturing same



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Patented Dec. 13, 1932 UNITED STATES PATENT OFFICE GEORGE A. RICHTER, OF BERLIN, NEW HAMPSHIRE, ASSIGNOR TO BROWN COMPANY, OF

BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE ARTIFICIAL LEATHER AND PROCESS OF MANUFACTURING SAME No Drawing. Application filed March 16, 1927,

In manufacturing artificial leather and like materials, it is common practice to impregnate a textile fabric base or foundation with rubber latex or a rubber solution, then to fix the rubber in the fabric by evaporation of the liquid vehicle or' solvent, and finally, if desired, tovulcanize the impregnated fabric. In like manner, it has also been proposed to impregnatepaper or .interfelted fibrous foundations. But interfelted foundation or base material comprising relatively short fibers, as heretofore made, has been found unsatisfactory for the production of artificial leather, doubtless because such short-fibered material, which is initially considerably weaker than a textile, is incapable of absorbing sufficient rubber to impart the necessary body, strength, tear resistance and elasticity of artificial leather; andeven the so-called paper felts prepared from cotton or wool her, or strong papers prepared from manila,

or rope fiber, or so-called sulphate pulp, are

of insufficient strength and absorptivity to produce a good artificial leather having optimum characteristics of weight, tear resistance, etc.

I have found that a paper web in which fibers, such as hereinafter described,-exist in interfelted but in uncompacted, loose condition, isso highly absorptive that, notwithstanding its lack of initial tensile strength,

it constitutes an excellent base or founda tion material for the manufacture of artificial leather. Such a paper web is preferably formedof unbeaten or'very lightly beaten fiber, as its absorptive capacity is eater when its fibers are unhydrated. By eaten fiber, I mean fiber whichlias been beaten orhydrated to produce a relatively slow stock 3 in which the individual fibers are more or less coated with cellulose hydrate or gel, and not Wood pulp or the like in the form as ordinarily purchasedi which has merely been disintegrated or in ividualized in a beater en- A paper" web such-as ,herein desired is formedby felting the unbeaten or lightly beaten fiber on a papermaking machine, and

removing water therefrom, preferably without compacting-its fibers, by subjecting it to Serial No. 175,946. Renewed October 25, 1932.

heavy suction or to mechanical pressuredevices, such assqueeze rolls. Such a aper web is thus formed under conditions di erent from those maintained during usual paper manufacture, wherein the'wet paper web is chines, e..g., a machine of the Fourdrinier,

type, may be employed, but the web is formed and allowed to remain on the moving wire until it is substantially dried; or, after partial dewatering, it may be transferred to another moving wire, upon which it is dried. For instance, after the web is formed, itmay be partially dewatered by passing it over one or more suction boxes or rolls maintained under light suction, but it is preferably not subjected to any mechanical pressure devices. While still on the wire, it is dried, as by passing it over a series of hot plates or over a series of drying rolls, preferably without The resultingdry' paper web is highly bibulous and absorptive, as its interfelted fibers exist in an uncompacted and loose and more or less fiufly condition. Such a web is not onl absorptive in consequence of the large voi orinterstices between the fibers, but also in consequence of the unbeaten condition of the fibers, which prevents material shrinking. Thus,'whereas a web formed of hydrated or beaten fiber, upon drying, shrinks considerabl and the cellulose hydrate on hardening 11s the pores and cells of the web, a web formed of very free stock, as herein described, shrinks but little and is hi hly porous and absorptive.

n preparing a bibulous-web such as described, I preferably use a high alpha cellulose-containing wood fiber, i. e., one which has a high proportion of alpha cellulose and is substantially free from oxyoellulose and other non-alpha cellulosic components. Such fiber is prepared by extracting or dissolving the non-alpha cellulosic material from chemical wood pulp (derived from the digestion of wood chips), by a series of treatments with chemical reagents without appreciably degrading the alpha cellulose content of such pulp, asdisclosed in patent application, Serial No. 716,154, filed May 27, 1924, by Milton 0. Schur and myself. Preferably, an al ha fiber derived from kraft pIulp as describe in myapplication, Serial 0. 73,193, filed December 4, 1925, is employed, as such fiber not only possesses high absorbency, but ossesses high strength and tear resistance, oubtless because of its long avera e fiber length. As disclosed in both the a ore-mentioned applications, the preliberated or chemical wood pulp is refined in an alkaline liquor to hi her alpha cellulose content, namely, an alp a cellulose content of at least about 93%. The high absorptive capacity of such alphapulp is doubtless a consequence of the highly cellular or porous structure of the individual fibers, as a result of the extraction of the impurities or nonal ha cellulose constituents from the fiber ce ls. A certain proportion of mercerized fiber, which ma be alpha or other fiber, may be incorporated in desired roportion into the web-forming stock.- e presence of such fiber is advantageous, as it is bulky and absorbent; and a web formed from such fiber undergoes very low shrinkage upon drying. Preferably, however, it is not used alone, as

it does not readily form or interfelt by itself into a web-of uniform texture on papermaking machines.

The dry, bibulous web produced as hereinbefore described may be readily impregnated with rubber by proper treatment. In one case, this is accomplished by passing the web through an a ueous rubber dispersion either in the form 0 natural rubber latex or in the form of an artificial dispersion or latex preportion, say, 2% to 5% of sulphur or Ifan artificial leather having rigidity or pared from crude or reclaimed rubber. The dispersion may contain, say from 10% to 30% rubber, and may also contain a suitable proequivalent when it is desired to produce a vulcanized product. Also, if desired, accelerators of vulcanization, fillers, pigments, resins, or other compounds maybe added to the dispersion in such proportion as will result in a product of the desired characteristics. In passing through the dispersion, the web becomes thoroughly soaked or im regnated therewith, whereupon it is passe through rolls which serve to remove only excess dispersion therefrom, without effecting an appreciable compacting of the web, the resulting rubber-dispersion-impregnated web be ing of the desired rubber content. The water of the dispersion may be removed by evaporation; or the web may be passed through a suitable coagulating medium, say, an acetic acid solution of 5% to 10% concentration, or through a coagulating atmosphere, such as acetic acid vapors, sulphur dioxide, or the like. Preferably, a coagulating'atmosphere is employed, as the coagulating vapor or gas penetrates the web more easily to yield a more uniformly permeated product and serves to coagulate and fix the rubber more satisfactoril on the fibers in the web. The

eater uni ormity of the product is due to the fact that by coagulating the rubber before a drying, migration of the dispersed rubber particles along with the water to the surface of the web, where evaporation takes place during subsequent drying, is avoided. Such migration is especially serious when theusual alkali-preserved latex of commerce or the usual artificial latices or dispersions are used in association with a highly bibulous web such as herein described, in which the, capillary action is especially high. In any event, however, the dis ersed rubber is preferabl coagulated in sltu in the voids and on the bers to produce a web permeated with coagulated rubber before drying. The resulting product has excellent so-called pl adhesion, or tenacity of bond between its ace portions or layers, high resistance being encountered to the pulling apart of the dried product after it has been split. If, on the other hand, considerable migration of rubber to the surface of the web takes place during drying, the center of the web is left relatively poorer in rubber and the web may easily be pulled apart after splitting. The web is then dried, as by passing it over hot rolls, or through a hot air tunnel. The impregnated web may be dried without previous coagulation of the dispersed rubber therein, depending on the condition of the dispersed rubber-component of the dispersion, that is, upon the tendency of the rubber particles to migrate during drying. Inasmuch, however, as coagulatiton of the dispersion in the web prior to drying apparently effects a more intimate and tenacious bonding together of the fibers, coagulation is preferably effected prior to drying.

multi-ply web is effected before firmness is desired, the rubber-impregnated web is subjected to vulcanization. The vulcanizing agent may be added to the aqueous rubber dispersion, as stated; and the rubberimpregnated web containing the vulcanizing agent may be dried at a sufficiently elevate temperature for a sufiicient period to produce the desired vulcanization. In other cases, in lieu of incorporating the vulcanizing agent into the rubber dispersion, vulcanization may be accomplished by passing the rubber-impregnated web through a vulcanizing atmosphere,-for instance, through an atmosphere of sulphur chloride vapors or through a vulcanizing solution, such as a solution of sulphur chloride in alcohol or carbon bisulphide, or through an atmosphere of hydrogen sulphide or one of sulphur dioxide, or successively through both atmospheres in theorder stated, or in reverse order, with or without the application of heat. In lieu ofan aqueous rubber dispersion as the impregnating medium, a solution of rubber in a suitable solvent, for instance a rubber-benzol solution of, say, 5% to 10% rubber content, may be used for such purpose. After impregnating the web and removing any excess solution therefrom, its solvent content may be evaporated and recovered.

When it is desired to produce a multi-ply artificial leather, a plurality of webs may be simultaneously impregnated with rubber. dispersion and then superposed and united as by piress-rolls prior to drying, but it is preferable. 35

rst to coagulate the rubber and then dry, since by passing the multi-ply web through a coagulating medium, a firm cohesion or bonding together of the contacting faces of the webs by the coagulated rubber is brought about. If the webs have been impregnated with a rubber solution, their union into a their solvent content is removed. i The important advantage in'fem loying a bibulous, uncompacted web formed of alpha fiber such as hereinbefore described is that the artificial leather product realized therefrom may have a rubber content of 100% or greater based on the dry weight of the web fiber, an yet simulate natural leather in its appearance, feel and other important physica qualities. Such one is markedly dissimilar to a product wherein a paper web, manufactured bynsual methods, serves as a foundation. For instance, the .usual blotting paper is far less absorptive than'the web herein employed as a foundation and does not in other respects answer the purpose of the present invention.

Similarly, a web which is open or porous owing to a loose or wild felting on a paper ma chine, but which has been compacted in the course of its manufacture, does not yield the artificial leather product herein desired, even when made of relatively long'fibers, forit' does-not possess the absorptivity andother qualities of a substantially uneompacted web, especially one made of the refined wood pulps hereinbefore described. An uncompacted web may be made from fiber of the order of length of wood fiber derived from spruce, for example, and yet possess, the absorptivity requisite for the production of the artificial leather product of the present invention.

tion was formed of a high alpha cellulose wood fiber prepared from sulphite spruce fiber.

Waterleaf Alpha 83m Blotting Paper fiber desk hard web-of but com blotter blotter present pacted invention Basis weight 21.4 232.6 211.0 24.1 Thickness (inches)--- 0034 0260 0225 0090 compactness 8Q 94 27 Absorptlvlty 90 to 150 180 130 500 exterpoluted. 300 in 1 5 min.

The compactness value hereinbefore given the bulk or thickness in inches, and multiplying by the factor 10- The absorptivitv was ascertained by noting the water crawl up a strip, the values given denoting hundredths inches crawl up the strip in five minutes. It is to be observed that the compactness of the web used in the product of thepresent invention is far less, and that its absorptivity is far vents, and accordingly by the term solvent .1 mean to include the aqueous phase of a-rubis obtained by dividingthe basis weight by ,sions, and. solutions of rubber in organic solber dispersion and also the organic-solvent of solutions of rubber.

It do not herein claim the-bibulous web per se, or the method of its manufacture, aslthis constitutes no part of the present'invention.

What I claim is: 1. An article of manufacture, comprising wood fiber with rubber latex, and coagulatingtheru'bber in site within the web bycon i "a loosely felted, uncompacted paper web. of a high-alpha cellulose-containing wood fiber "loosely felted,- uncompacted paper web of tact with a gaseous coagulating atmosphere.

3. A process which comprises saturating a loosely felted, uncompacted paper web of wood fiber with rubber latex, coagulating the rubber in situ within the web by contact with a gaseous coagulatin atmosphere, and drymg and vulcanizing t 1e web.

4. A process which comprises forming a cellulosic fibrous paper web in which the fibers exist in a loosely felted, uncompacted condition, saturating said web with acetone, evaporating the acetone, permeating the web with rubber, and vulcanizing the rubberpermeated web. 5. As an article of manufacture, a web of inter-felted cellulose fiber, at least a portion of which is mercerized, impregnated with rubber.

6. As an article of manufacture, a web of loosely felted, uncompactcd cellulose fiber,

at least a portion of which is mercerized,

impregnated with rubber.

7 A process which comprises impregnating a bibulous web of fiber with rubber latex, coagulating the rubber in situ in the web by contact with fumes of acetic acid, and drying the web.

8. A process which comprises impregnating a bibulous web of fiber with rubber latex,

coagulating the rubber in situ in the web by contact with sulphur dioxide, and drying the natin the felt with a rubber-carrying liquid vehlc e, and drying the impregnated felt.

14. A process which comprises refining preliberated chemical wood pulp in an alkaline liquor to a higher alpha cellulose content, forming a waterlaid, absorptive felt rom a furnish containin such refined wood pulp in a substantially unliydrated condition, lmpregnating the felt with latex, and drying the im regnated felt.

15. process which comprises refining preliberated chemical wood pulp in an alkaline llqlOI to an alpha cellulose content of at least a out 93%, forming a waterlaid, absorptive felt from a furnish containing such refined wood pulp, impregnating the felt with a rubber-carrying liquid vehicle, and

drying the impregnated felt.

16. A process which comprises" refining preliberated chemical wood pulp in an alkaline liquor to an alpha cellulose content of at least about 93%, forming a waterlaid, absorptive felt from a furnish containing such refined wood pulp in a substantially unhydrated condition, impregnating the felt with latex, and drying the impregnated felt.

17. A process which comprises forming a felt from a fiber furnish containing mer cerized cellulose pulp. impregnating the felt with a rubber-carrying liquid vehicle, and

drying the impregnated felt.

18. A process which comprises forming a waterlaid felt from a fiber furnish containing mercerized wood pulp,.impregnating the felt with latex, and drying the impregnated felt.

In testimony whereof I have afiixed my signature.

GEORGE A. RICHTER.

10. A rocess which comprises impregnat- I ing a bi ulous web of interfelted cellulose fiber with a volatilizable liquid having a much lower surface tension than water alone to swell said web, drying the web to remove said liquid under said lower surface tension and thereby to enhance the porosity of said web, impregnating the dry web with a rubbercarrying vehicle of a liquid nature, and removing the vehicle.

11. As an article of manufacture, a rubberimpregnated, loosely felted fibrous web, comprising refined wood pulp having an alpha cellulose content of at least about 93%.

12. As an article of manufacture, a rubberimpregnated, felted fibrous 'web comprising substantially unhydrat'ed, refined wood pulp having an alpha cellulose content of at least about 93%.

'1-3. A process which comprises refining preliberated cellulose pulp in an alkaline liquor to higher alpha cellulose content,

forming a waterlaid, absorptive felt from a furnish containing such refined pulp in a V substantially unhydrated condition; impreg 

